An X-ray is an electromagnetic wave having a short wavelength corresponding to a wavelength band of 10 to 0.01 nm and a frequency band of 30×10 15 to 30×10 18 Hz, and shows straightness, penetration, and attenuation that X-ray is attenuated according to an X-ray attenuation coefficient unique to a substance in the process of penetrating through the substance placed in a path of the X-ray.
X-ray radiography is a radiography method using straightness, penetration, and attenuation of X-rays, and based on the amount of attenuation accumulated in the course of the X-rays passing through an FOV (field of view), it displays a gray-level X-ray image of the internal structure of the FOV. To achieve this, an X-ray imaging apparatus includes: an X-ray source configured to irradiate X-rays to an FOV; an X-ray sensor configured to detect X-rays that have penetrated through the FOV; and an image processor configured to reconstruct an X-ray image of an internal structure of the FOV by using X-ray projection data, as a detection result detected by the X-ray sensor.
In recent years, X-ray radiography has been rapidly evolving into DR (Digital Radiography) using digital sensors due to the development of semiconductor and information processing technologies, whereby image processing technology has also been developed and is used in various ways according to the purpose and application field.
FIG. 1 shows a panoramic X-ray image that is mainly used in the dental field.
As shown in the drawing, a general panoramic X-ray image displays an arrangement relation between a tooth and tissue therearound of any image layer in the dental arch, as a two-dimensional transmission image. Accordingly, the panoramic X-ray image is used as a standard image most familiar to dentists because it can be used to easily identify the overall arrangement of a tooth and tissue therearound with only a single image.
Further, to obtain the panoramic X-ray image, the focal interval between the X-ray source and the X-ray sensor is shifted along any image layer in the dental arch, thereby acquiring X-ray projection data for each section of the image layer, and the X-ray penetration data is appropriately superimposed on a two-dimensional plane to form a panoramic X-ray image for the image layer.
FIG. 2 is a schematic view showing a general panoramic X-ray imaging apparatus.
As shown in the drawing, a general panoramic X-ray imaging apparatus roughly includes: a radiography unit having an X-ray source 12 and an X-ray sensor 14; and an image processor 40 configured to realize a panoramic X-ray image based on a detection result detected by the X-ray sensor 14. Further, the radiography unit includes: a rotating arm 10 configured to position the X-ray source 12 and the X-ray sensor 14 to face each other with a subject 1 therebetween; and a driver (not shown) configured to rotate and move the rotating arm 10 about a rotating shaft 11 between the X-ray source 12 and the X-ray sensor 14.
Here, the driver of the general panoramic X-ray imaging apparatus is performed by a two-axis drive system, which is configured to rotate the rotating arm 10 about the rotating shaft 11 and linearly move the rotating arm 10 along a plane perpendicular to a longitudinal direction of the rotating shaft, such that the focal interval between the X-ray source 12 and the X-ray sensor 14 is shifted along any image layer in the dental arch.
However, the two-axis drive system of the general panoramic X-ray imaging apparatus has several problems.
For example, for two-axis driving, two or more driving sources, such as a motor, being in cooperation with each other are required, and particularly, for constant superimposition of the X-ray projection data, the shift interval of the X-ray source 12 and the X-ray sensor 14 should be precisely controlled. Due to this, the entire configuration of the apparatus becomes complicated and large, and also, rotation speed, movement speed, and trajectory are limited. Accordingly, the radiography time is lengthened and the amount of radiation applied to the subject is increased, and the possibility of interference such as collision with the subject is always involved.